Sludge coking process



Nov. 25, 1941.

C. D. FENTRESS ETAL SLUDGE GOKING PROCESS 2 Sheets-Sheet l Filed Nov. s,1938 inw l Nov. 25, 1941.I cy D. FNTESs E-rAL i `2,263,765

sLUDGE coKING PROCESS Filed Nov. 9, 1938 2 Sheetsf-Sheet 2 SPRAY emmenSETI'LING TANK Mw.Y

VClan/df. I? lc/Veil Edwin G. Wiley Patented Nov. 25, 1941 UNITED STATE15@ FTENT QFFICE i SLUDGE Cllirnss" i f Whiting. and Edwin G.WileyyHammondJnd-s, assignors to Standard Oil Companyg. Chicago,u

111.,.a corporationoflndiana Application November 9, 1938,T Seniat-Nu.4.?}39`=,6.Z,0J

(c1. zs-.nm

1 Claim..y

This invention relates to the col'ng of acid sludge and to the recoveryof products suchv as coke, oil and sulfur dioxide therefrom.

Sludges produced the acid treating of' peV troleum oils have longpresented a seriouspr'oblerny since it is difficult to disposeotthem'and since-` it is desirable to` recover therefrom valuf ableproducts such asv oil, coke and sulfur dioxiidey for sulfuricacidAmanuf'acture or' otherl use: One processv which has* been designed tosolve this problem involves the heating of the acid" sludge in thepresence of'4 hot. cokeV to produceA furtherh cokev therefrom and todrive oit products including sulfur dioxide and cilwhich. can

be recovered forI use;

It` is an object of our invention to: provide imjproved methods andapparatus for the coki'ng" of acid sludge. A more detailed' object ofour invention is to provide' methods andi apparatus Y for cokingn acidsludgel which will give an' in"- creased recovery or', in other; Words",decreased l'oss ofl sulfur dioxide. A further object-of our' inventionis to provide such processes and apL paratus with a View to decreasingthe arrnountv` of sulfurfdi'oxidel sent to the sewerY or to' the-Vatmospheresince contamination ofsewage or the atmosphere is undesirable.Other and more2' detailed objects, advantages andl uses of' our in'.-vention Will become apparent as the description thereof proceeds;

While this invention is susceptible, to numerous embodiments, onespecific embodiment is shown in the accompanying' drawings, Figure I andFigure 2 taken together representing a sirn-` plied flow diagram. Figure1 represents chiefly the sludge conversion process. and` Figure 2 the:

purification orv the sulfur dioxide' therefrom.

Other* modifications: will occur to' those skilled" in the art and areintendedl to be covered" to the extent thatthey fall Within the scope ofthe appended claim.

Acid sludge from the. acid treatment. of oil's or otherv source isconducted throughv line to" sludge-receiving vtank I'I. Steam coils' l2-are located about sludge-receiving tank toi provide necessary heat and"sludge may be circu# lated through lines I3 and |,4 byV rneansof'pumpAl5' for mixing'.

Sludge is conveyed through valve f6 i'n. line I1 from line I4 by meansof charging pump |'3" and line |9' toi sludge decomposer 2`0 whereinuity is subjected to the actionV of hot coke;

Additional sludge differing iny physicalcharacteristics from thatreceived' in sludge-receiving tankl may be conveyed from any-k suitable'kilnV 3| opposite the" coke entrance:

source to'j tank' 2li This slud'gemay iecircu'- passage 364 to sludgedecomposer'z" where itf i's' injected byrmea'ns ot plunger feeder` 3T.Dust from they cokeL which` mayb escapev from passage 36| is collectedthrough:` line 318i whichV joins eline" 39': from the exit of' sludgeydecomposer'zi). A dust-removal system 41TV having a water spray'l Mland' a fan system 42 serves' to remove4 the dust from lines 3'8' and39;` Vent 43j permits the'escapeiofgases and any unremoveddust While theremainder of" the dust' plus`V the waterA from sprayl 4| is,i ledthrough lines I44 or" 4'5" toline @d which leads to; disposal means.

` From coke-heating kiln 3| excess flue gases` escape through vent 4Twhich is cooledI by water sprayI 481 To` remove` any entrained dust: or"coky materiali which' may rise back of baffle: Walt d'9,` water is;injected through spray" 5|);A the dust-laden Water being delivered todisposal means through linev 5 The products of decomposition,consisting'of coke and gas containing sulfur; dioxide,I hydrocarbons;Water vapor; carbon dioxide,7 air.,` dust, etc., exit. from'. sludgeclecornposer 20' through` stationary header- 52".y Coke is conveyed topas"- sage'.` 53: by means of plunger feeder 54 thence to elevator 55which may be ofthe bucket type. The. coke canv be cooled by Water fromspray 5B' andi canv beA further quenched.v by. steam from .linel 5.12Coke.= raised through bucket.` elevator 5,5@` passes. to dust.lcollector hood 5B fromwhich leads line` 59 which joins line 39 andpasses. tm` dust-removal systemv 40.V The coke: is. conveyedl byv cokevconveyor 601', which canbe of thev endless-belt type; to: feedfhopper'29; 'Iliat` part ofV the coke notnecessary` forreturrr toIcoke-heat* ing kiln 3| passes to coke conveyor 6L' which# leads tolcoke'disposal? bin` B21; The cckevon` cokeconveyor 6| can be cooled byspraying withwater` from spray 63E @oke from coke-disposal bin 62 can bedumped intocars El; which aresprayed with water from spray 65, forremoval from the system.

Gases from stationary header 52 are conveyed by line 66 to scrubbingtower 61 where they impinge upon cooling liquor. Cooling water and/orsteam can be injected through line 68 from lines 69 and/or 18 foremergency cooling. Cooling liquor is injected into scrubbing tower 61through line 1| terminating in sprays 12. A continuous overflow unit 13or an intermittent overflow unit 14 may be used for the removal of waterand condensed material from tower 61. 'I'his material passes throughlinesy 15 or 16 to line 11 which leads to a separating means 18,preferably of the Dorr classifier type.

Cooled gases are carried overhead from scrubbing tower 61 through line19 having damper 80 which controls the vacuum in the system, and jugvalve 8| for shutting off one unit if two or more scrubbing towers 61are used with cooling tower 82. This tower is supplied with coolingliquor through line 83 and spray 84. Emergency water is supplied throughline 85 and sprayV 86. The cooling liquor may be removed from coolingtower 82 by line 81 Ywhich leads to liquor-cooling tank 88.

Condensed oil is withdrawn from cooling tower 8 2 through overflow sealbox 89 and line 98 which leads torliquor cooler 88. Line 9| which leadsto suitable disposing means is used for draining the tower in emergency.Overhead gases from cooling tower 82 are passed through line 92 to oilseparator 93 which is equipped with spray 94 for dispersing coolingmedium from line 83 and line 95. Emergency water spray 96,thermostatically controlled, prevents unduly high temperatures at thegas exit. The condensed oil and liquor iiow through line 91 to line 81and thence to liquorcooling tank 88 for further cooling.

The gases from oil separator 93 are taken overhead through line 98 andblower 99 to sulfur dioxide furnace |08 having suitable'baiiiedcheckerwork. Inserted in line 98 between blower 99 and sulfur dioxidefurnace is a vent |0| and a Water seal |82 for the prevention of blowback from sulfur dioxide furnace |88, when the plant is not in operationand the furnace is being heated. Gases pass into sulfur dioxide furnace|08 about baille wall |03 to contact the heat from burner |04. Thisburner can be fired by means of gas through line |85 or oil through line|06 and steam through line |01 which lead to line |08. Blower |09 addsair 'for the combustion of the uncondensed hydrocarbons. Sulfur dioxidefrom sulfur dioxide furnace |00 passes through duct ||0 (having vent forstarting up only) to spray chamber ||2. Cooling liquor from line 3sprays through spray ||4 to Vcool the gases from furnace |80. The waterwith dissolved sulfur dioxide is removed through line 5 having automaticoverflow control |6 to liquor-cooling tank ||1. Sulfur dioxide gaspasses through line ||.8 and is further cooled in spray tower ||9,equipped with ring packing, and taken overhead through line to anysuitable system for converting the sulfur dioxide to sulfuric acid, etc.

Liquor from spray tower ||9 passes to liquorcooling tank |2| throughline |22 and is recirculated to the spray tower ||9 through line |23 andpump |24.

Fresh water may be added for additional cooling in the spray towerthrough line |25. Excess liquor passes through valved line |26 to line83 and cooling tower 82.

Cooling water is supplied to liquor-cooling tanks 88, ||1 and |2|through lines |21, |2111, |21b and |21c, and discharged to the sewerthrough lines |28a, |2812 and |280. The liquor from cooling tower 82 andoil separator 93 is partially separated in liquor cooling tank 88.Excess liquor from cooling tower 82 can be withdrawn from line 81 anddirected to scrubbing tower 61 through line |29 and line 1|. he oil andcondensables present plus excess water flow to settling tank |38 throughline 3| where a further separation between water and oil is made. Theseparated water ilows to the sewer through lines |32 or |33 and theseparated oil is conveyed to dark oil tank |34 through line |35. Thecooled liquor from liquor-cooling tank 88 is recirculated through line83 and pump |36 to cooling tower 82. Cooled liquor from liquor-coolingtank ||1 is recirculated through line 3 and pump |31 to spray chamber 2which is equipped with emergency draw-off line |38 which leads to thesewer. In separating means 18 the contaminated liquor from scrubbingtowerl 81 is separated into oil, water and a coke-water slurry. Skimmedoil is sent to dark oil tank |34 through line |39.

, The coke-water slurry can be returned to cokeheating kiln 3| throughline |40 and pump |4| or withdrawn for use as fuel outside of the sludgeconversion unit through line |42. Water is recycled to scrubbing tower61 through spray 12 by means of line 1| and pump |43 or vented from thesystem to the sewer through line |44.

Dark oil from dark oil tank |34 may be supplied as fuel to burner 32 bymeans of lines |45 and |46 through pump |41 to line 34 or to burner |84through lines |48 and |49 by means of pump |50 and line |08 or may beused elsewhere as fuel.

In carrying out our process with the above or similar apparatus sludgeacid from the treatment of hydrocarbon oils, particularly sludge acidfrom the treatment of oils in the manufacture of lubricating and whiteoils, enters through line |0 into sludge-receiving tank Since thissludge acid may have a tendency to separate into an oil phase and anacid-carbonaceous material phase, if vallowed to stand, it is desirableto keep the contents of the sludge-receiving tank agitated. This may beaccomplished by circulating the sludge through lines I3 and |4 by meansof pump |5 so that a continual mixing occurs. The contents ofsludge-receiving tank are heated by means of steam coils I2, or anyother suitable means, in order to decrease the viscosity of the sludgeand permit it to be circulated more easily. Open steam within tankshould not be used for heating purposes, however, since this will tendto hydrolyze the sludge, separating out the acid and permitting a hard,coke-like layer to form in the receiving tank which is extremely diicultto remove.

The well-mixed sludge which has passed through line 3 to line I4 is sentthrough valve |6 and line |1 to the sludge decomposer 20 by means ofcharging pump I8 and line |9.

Sludge from the treating of other hydrocarbon materials of a differentnature such as, for example, the treatment of light oils, which is to alarge extent mmiscible or only slightly miscible with the type of sludgesupplied through line I8, or which because of its more dilute nature maytend to hydrolyze the sludge in sludge-receiving tank llumay be storedin sludge tank 2|, This latter sludge acid may be made homogeneous andkept thoroughly mixed by recirculating means similar to that employedwith sludge-receiving tank and illustrated by pump 22 and line 23.

The sludge acid from sludge `tan-k I2'I vmay be added fto thesludge acidvfrom sludge-receiving tank LII by injecting itintolineI1just:ahead o'fchargingfpump 4H3. In so doing valves .24,125 and 21 lshouldbefsoradjustedthat a major portion of the sludgeflows through line 28 toli-ne I.1 and at the `same :time circulation of the sludge through vtank2I maintained. On the other hand, the sludge acid'from sludge tank '2 Imay 'be sent directly `to sludge `decomposer L29 by means of line`26. Inthis case valves .24, and.2'1are likewise adjusted l to permitcirculation `of sludge inftank-ZI --and to :regulate the'flow of sludgeIto thedecomposer-.

"Cokeffrom any suitablesource is led from feed hopper .12:9 `tocoke-heating kiln 3l. When the process is .first started `up coke may besupplied from any outside source and is preferentiallypetroleum coke.When the .process is in continuous operation, however, the coke from thedecomposition of thesludgemay be and preferentially is recycled to thefeed hopper. The coke is aided in its passage vfrornlfeed hopper 29 byvibrating feeders 39 which assist in theveven and regular rate ofdistribution of the coke to coke-heating kiln 3i.

Coke-heating kiln 3l is of the rotating type making approximately fourrevolutions per minute. Thecoke is heated by means of burner 32.Thisburner may use either gas, or oil and steam, as vfuel and, asshown,is so designed 'that these fuelsmay be used interchangeably, gasbeingfed throughl line 33 while `oil and `steam enter through lines 34 and'5respectively. The coke is heated to the proper temperature which shouldbe from about `990 F. .to about 1200 F. Flue gases plus any volatilematerial obtained from the heating of the coke pass under bridge wall 49and are vented to the atmosphere through vent 41. A water spray r5E!helps to cool .the exiting vgases somewhat, as well as remove entrainedparticles and dust from the coke. Water 'spray 43 aids in furthercooling the exiting gases, thereby minimizing danger of. lire fromexcess heating of overhead enclosures, etc.

In sludge decomposer 2i), which is also of the rotating type, the hotcoke from coke heating kiln -3I Vdecomposes the sludge acid. Thedecompositionfproducts generally consist of sulfur dioxide,volatilehydrocarbons, water vapor, carbon dioxide, air and coke. Thecoke falls to the .bottom of .stationary header :52 and the remainder ofthe decomposition Aproducts pass overhead through line B9. Feeder 54forces the coke throughipas sage 53 to bucket elevator 55. As it exits,the coke has a temperature range of approximately 350590 F. In order tocool the coke, water can be supplied through spray 56 and furtherquenching .by means of steam can be accomplished by injecting steamthrough line 51. The coke is carried upward by bucket elevator to cokeconveyor 60 where it is returned to feed hopper 29.

Feed hopper 29 is so designed that coke in excess of that usable in theprocess is sent by means of conveyor 6I to coke disposal bin 52. Spray63 may be used for spraying water on the coke on .conveyor 6Ifor'further cooling and dust laying. The coke from coke disposal bin 62may be ref moved from the system by means of coke car 64 -or a similarmeans. Water 'from spray 95 is .used for laying dust from the coke incar 64.

Because'it is notpractical to assure air-.tight fittings at the pointswherethe coke enters'and leaves `sludge decomposer 29 and because thelpresence `.of Ilarge amounts of `dust in the :air :.is

,- poser l29 `and the intervening connections.

lcooling tower.

`extremely hazardous, `a dust removal system .is supplied. A'I'langedduct leadsirom` the .feeder to bucket elevatorl55 `to line `39 and asimilar flanged duct from feeder A31 leads to line 38 which joins line.'39 :and 'passes fto dust-removal system 49. In addition, dust from thecoke as it is deposited on Vcoke Yconveyor .'60 from bucket elevator 55is collected inconveyor'dustzhood 58 from which it passes through line59 to line 39 and dust-removal system 40. Water from water spray 4Iindustremoval Jsystem 40 tends to Vremove a .large portion ofthevcollected dust. .Thisdust-watermixture may be removed fromdust-removal system '4D by line 44 from the base of dust-removal-sysvtem40 or'bylineflIE which leads Afrom an overflowfsystern =in dust-'removalsystem 49 through line '46 to the seweror-other suitable disposingmeans. Affari 142 tends torplace sufcient suction .on the dust-remova1system 40 .and connecting lines `E3B, 4239 Vand 459 to removefthegreater lpart of the dust. The comparatively dust-.free air is vented tothe atmospherethrough vent 43.

Thesuluredioxide, 'volatile hydrocarbons, water vapor, carbon dioxide,vair plus some dust `and light particles carried `along by entrainmentpass overhead -from header 52'through'line 69 toscrubbing .tower 1,61 inwhich the dust and `the -heavier of the `volatile hydrocarbons areremoved. VThese less vvolatile components impinge upon a liquor layer`in scrubbingtower 91 which is supplied from line 1I Yand-spray .12withcirculating liquor which willbedescribed'in greater detail later.The.liquor level in scrubbing tower 61 mayfbeV controlled by continuousoverflow means 13 and line 15 or intermittent overlow'means 14 andlineV16. An emergency spray 58 is provided for 'further coolmg.

The `heavier hydrocarbons, coke particles, dust, :etcghavng beenremoved,.the overhead gases pass through conduit 19 to cooling tower82,`lled with checkerwork. These gases are at approximately 180 F.

A hand control damper 89 actsto maintain the proper vacuum on scrubbingtower 61, decom- Jug Valve 8|, in line 19, is=usedto shutoff one of theunits rinxcases where two ormore units utilize one The volatile`material is further cooled in `coolingtower 8.2 by liquor from line 89and spray 84, aswell as water from emergency line and emergency spray 86if necessary. This procedure will furtherrernove ccndensablehydrocarbons. The water level in cooling tower 82 is maintained at anydesired height so that the gases vfrom line 19 :impinge upon it andtheexcess is led through line.81 and liquor cooling tank 88 where it iscooled to approximately'QWfF. and returned through line 83 by means ofpump L35 touspray 84. 'Naturally as a certain amount of sulfur dioxideis absorbed in the water in cooling tower 82, byrecirculating itthroughliquor cooling tank 88 and thereby avoidingdiscarding it to .thesewer, the minimum amountof sulfur dioxide will be lost.

It is extremely important that a liquor vsaturated with sulfur`dioxide-be used. For example, the stream of volatile material fromdecomposer 20 contains approximately 50% sulfur dioxide. Water at F. andat one atmosphere pressure, under these conditions will containapproximately 0.2% sulfur dioxide. At 104 F., however, the Water willcontain approximately 3.2% sulfur doxide. .It can be seen, therefore,that the discharge of cooling 4water from scrubber 61 atthe Vhighertemperature will mot Wentail -anygreat z-lcss of sulfur dioxide to thesewer, but the use ofcontinuous fresh water for cooling in cooling tower82, with subsequent discharge of the saturated water at approximately100 F. would entail a loss of aY substantial amount of valuable sulfurdioxide. By recirculating the sulfur dioxide saturated water throughcooling tower 82, further absorption of sulfur dioxide is avoided, andthat present is not discharged from the system.

The wash water removed from scrubbing tower 61 for discharge from thesystem should be at a temperature of at least about 150 F., andpreferably above 170 F.

This is also true to a lesser extent in spray chamber ||2 and spraytower H9. The sulfur dioxide stream from furnace |88 containsapproximately sulfur dioxide. The exiting liquor from chamber ||2 is atapproximately 140 F. and will contain about 0.4% sulfur dioxide. Theexiting liquor from tower ||9 is at approximately 115 F. and willcontain approximately 0.7% sulfur dioxide dissolved therein.

In order to prevent the fouling of cooling tower 82 by entrained taretc., which may not be removed in scrubbing tower 61, a cleaning means(not shown) may be inserted in line '|9. This may take any one of anumber of forms, for instance, it may be of the bag type or it may be athermal or an electric dust precipitator, or even of the cyclone cleanervariety. Any effective means for removal of dust and entrained materialmay be employed which will serve to prevent the fouling of cooling tower82.

The gases pass overhead from cooling tower 82 through line 92 to oilseparator 93. Oil separator 93 is also lled with a checker work ofacid-proof brick and a further separation of the condensed hydrocarbonsfrom the sulfur dioxide may be accomplished. Additional cooling isprovided by water from spray 94 from line 95 and line 83. An emergencywater spray 95, having a thermostatically controlled valve, in line 98,prevents excessive exit gas temperatures. Generally there is only aslight difference in temperature between the exit gases from coolingtower 82 and the exit gases from oil separator 93. Th'e overhead vaporsfrom oil separator 93 will now consist chiefly of sulfur dioxide, watervapor, air and a few last traces of hydrocarbons.

These gases pass by line 98 to furnace |88, asi sisted by blower 99,which serves to draw the decomposition products from decomposer 28,spray tower 61, through cooling tower 82 and oil separator 93 and theconnecting lines. Water seal |82 may be used in order to prevent hotgases from blowing back during the period when sulfur dioxide fromfurnace |88 is being brought up to temperature prior to actualoperation. Water is removed from the seal during operations.

In furnace |88 the last traces of hydrocarbons and non-condensables areburned out, heat being supplied from burner |84 which may use gasthrough line |85 or oil and steam through lines |86 and |81 respectivelyas fuel. Blower |89 supplies air for combustion. In place of gas or oilsulfur may be burned to provide additional sulfur dioxide as well asheat for combustion. Vent is provided for ventin-g gases during theperiod when the furnace is being heated prior to operation. When comingon stream the gas is vented to the air through valved vent stack |8|until the composition of the gas stream on the upstream side is outsidethe explosive range. The gases exit from furnace |88 through line til)H0 at about 1600 F. "Ihese pass to a two-stage cooling system consistingof a spray chamber 2 and a spray tower 9. Cooling water is suppliedthrough line ||3 and spray ||4 while a proper level of liquor ismaintained by overflow means H6 to which is connected line H5. The hotgases impinge upon the liquor surface and are sprayed and will exitthrough line ||8 at about 150 F. Further cooling in spray tower ||9 bywater through line |23 reduces the temperature of the exit gases toapproximately F. The sulfur dioxide, free of hydrocarbons and extraneousmaterial exits from spray tower ||9 through line |28 where it passes toany conventional system for converting the sulfur dioxide to sulfuricacid or to a compressing and cooling system for the formation of liquidsulfur dioxide.

Since in a process of this nature a considerable amount of by-productsare formed which are not directly usable in the manufacture of sulfuricacid, it becomes advisable to provide means for their recovery anddisposal. The bottom product from spray tower 61 will consist ofcondensed oils and hydrocarbons, water saturated with sulfur dioxide,and a certain amount of coke and dust. This passes through line 'il to aseparator means i8. Here the bottom product is separated into a lightoil or skimmed oil which will flow overhead through line |39 to dark oiltank |34. A bottom product consisting of a slurry of coke and dust andwater can be forced through line |48 by pump |4| to cokeheating kiln 3|,or can be sent elsewhere for use as fuel through line |42. The additionof this slurry of water and coke to the coke-heating kiln 3| may beadvantageous, however, because by cooling the incoming coke, a certainamount of soot prevention is obtained as well as better combustionconditions. The water which is saturated with sulfur dioxide is returnedby line and pump |43 to the spray in scrubbing tower 6l where it servesto cool further the incoming gases from sludge decomposer 28 and line66.

The heavy hydrocarbons separated in cooling tower 82 are furtherseparated into water and oil in liquor-cooling tank 88, the water beingreturned through line 83 and pump |36 to act further as a cooling mediumin cooling tower 82, while the oil is led by line I3! to settling tank|38 where it is further allowed to separate and the oil taken overheadthrough line |35 to dark oil tank |34 while the water, small in amount,may be sent to the sewer either by line |32 or, when it is desired toflush the tank, through line |33. The bottom liquor from spray tower i9passes by line |22 to liquor cooling tank |2| and is recirculatedthrough line |23 and pump |24 to spray tower ||9 to act further as acooling medium. Cooling water to liquor cooling tanks 88, and |2| issupplied by lines |21, 1.27ct, |2119 and ific, and may be discharged tothe sewer through lines |28a, |28b and |280. Excess overflow fromcooling tank |2| may be sent to liquor cooling tank ||1 where it mingleswith the liquor from spray chamber ||2 and is returned to spray chamberH2 for use as a cooling medium. Excess liquor from line |23 may bediverted to line 83 and cooling tower 82 by means of valved line |28.

The heavy hydrocarbons known as dark oil may be used as a part of thefuel in burner 32 or in sulfur dioxide furnace burner |84 or may be sentto storage. If the oil is to be used in burner 32 it passes from darkoil tank |34 by means of lines |45 and 34 through pump |41. Mixing withsteam from line 35 occurs just prior to its injection as fuel in burner32.

If the cil is to be supplied to burner IM then it will pass through lineIli and pump |50 to lines |48 and It where it is mingled with steam fromline |01 with or without oil from line |05 and injected into the burnerthrough line |68.

Although separating means 78 may be any effective means for separationof the oil-watercoke mixture, we find it highly preferably to use a Dorrclassifier. On the other hand, however, it is quite possible to use asettling box, or preferably a bed of fine vmaterial, through which themixture is allowed to lter. We have found that a bed of fine coke fromthis process is particularly eiective for the removal of coke and tarrymaterial from this by-product mixture.

Excess wash liquor is discharged from the system through line IM. Sincethe exit wash liquor from scrubbing tower iii is at a temperature aboveabout 150 F. and preferably above about 170 F., the amount 0i sulfurdioxide lost will not exceed about 0.4% of the amount available from thesludge decompcser 20. Actually, it will be much less than this sinceonly a small part of the wash liquor is discarded. Moreover, excess washliquor from cooling tower 82 and oil separator 93 nds its way toscrubbing tower 61 via lines Si, 91 and |29, and and excess wash liquorfrom spray chamber ||2 and spray tower H9 finds its way to cooling tower82 via lines |23, |26 and 83 and thence to scrubbing tower 61 with theother wash liquor from cooling tower S2, all of which is discharged atabove about 150 F. and then separated in separating means 78, withdischarge, if necessary, through line |44, thereby eliminating any lossof sulfur dioxide in the cooler wash liquors from towers 82u93, I2 andI9.

Although we have described our invention as having only one coke-heatingkiln, one sludge decomposer, etc., it should be understood that it isnot only possible but usually desirable to include two or more units sothat there may be continuous and uninterrupted operation. In the processof the type described, therefore, there would be two or more vibratingfeeders 30 to coke-heating kiln 3|, with their accompanying blowers,fuel lines, plunger feeders, dust collectors, etc., two or more sludgedecomposers with feed supply lines, exit lines, bucket elevators, etc.,as well as two or more original scrubbing towers. We have found that ina dual system after the preliminary scrubbing towers, a single coolingtower and oil separator, as well as a single sulfur dioxide furnace, issufficient to handle properly the volatile products from the sludgedecomposer.

We claim:

In a sludge coking process including decomposing acid sludge with hotcoke from a heating kiln fired by an oil burner, and washing theeffiuent vapors from said sludge decomposition with water to condenseoil vapors'and precipitate coke particles, thus forming a wash liquorcomprising water, oil, and coke particles, the improvement comprisingseparating said wash liquor into three fractions comprising respectivelythe bulk of said oil, the bulk of said coke particles, and the bulk ofsaid water, directing said oil fraction to said oil burner, directingsaid coke fraction to said coke heating kiln, recycling a major portionof said separated water fraction to said rst washing step andeliminating a minor portion of said water fraction at a temperatureabove F. to minimize sulfur dioxide solubility therein, again washingthe vapors passing said irst washing step with water at a temperaturelower than that of said first washing step to recover additional oil,separating said recovered oil from said second wash water, recycling amajor portion of said separated second wash water to said second washingstep and directing a minor portion of said separated second wash waterto said first washing step.

CARROLL D. FENTRESS. CLAUDE P. MCNEIL. EDWIN G. WILEY.

